Recently, with increasing sensitivity of color photographic light-sensitive materials, night photographing and photographing of sport scenes, etc., in which a high speed shutter is needed have become possible Moreover, the portability of cameras has been increased by miniaturization of films. This is due to an advance in techniques to improve granularity, resolving power, and sharpness.
The reason for this is as follows:
As is well known, in order to increase the sensitivity of silver halide light-sensitive material, it is necessary to increase the size of silver halide particles. This will lead to a reduction in granularity and a decrease in resolving power. When a negative film is miniaturized, the degree of enlargement at the step of printing must be increased. This will inevitably lead to a reduction in granularity and decreases in resolving power and sharpness.
Thus, in order to further increase the sensitivity of films and expedite the miniaturization, it is necessary to develop greatly advanced techniques.
Various methods for increasing the granularity and sharpness of color photographic light-sensitive materials have heretofore been known. For example, a technique for increasing granularity is disclosed in U.S. Pat. No. 3,726,681 which discloses a method in which in an emulsion layer of higher sensitivity of two layers which are sensitive to the same color, a coupler undergoing a coupling reaction at a higher rate is used, and in the other emulsion layer of lower sensitivity, a coupler having a lower rate of coupling reaction is used. U.S. Pat. No. 3,843,369 discloses a light-sensitive material in which at least one of blue-sensitive, green-sensitive and red-sensitive layers is composed of three layers, the top and intermediate layers of which have a color density of up to 0.60; and British Patent No. 2,083,640A discloses a method in which such couplers which produce slightly diffusing dyes through a coupling reaction are used to provide controlled smearing to dye cloud. The last technique is certainly effective for improving granularity, but it has such a defect that the sharpness grows worse. Therefore, the recent request on improvement of both granularity and sharpness is not sufficiently satisfactory.
A technique of increasing sharpness is described in U.S. Pat. No. 3,409,433 in which films are dyed with water-soluble dyes to prevent irradiation. A method described in U.S. Pat. Nos. 3,148,062 and 3,227,554 uses compounds which undergo a coupling reaction with oxidation products of color developing agents, producing dyes and at the same time, releasing development inhibitors; and a method described in U.S. Pat. No. 3,632,345 in which substances capable of coupling with oxidation products of developing agents, releasing development inhibitors without the formation of dyes are used (these compounds have heretofore been called "DIR compounds"). In addition, U.S. Pat. No. 4,248,962 and Japanese Patent Application (OPI) No. 56837/72 (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") disclose a method for improving sharpness with using DIR compounds releasing development inhibitors having high diffusibility. This method can improve sharpness to a certain extent, but this improvement is not yet sufficiently satisfactory. Conversely, the use of such DIR compounds releasing development inhibitors having high diffusibility gives rise to the problem that granularity is rather reduced.
In view of the above-described technical situation, difficulties are encountered in improving sharpness and granularity simultaneously. This is because when compounds to improve sharpness and granularity are used in combination, they exert adverse influences on each other, reducing their own effects.